Electrostatically driven low-voltage micromechanical RF switches using robust single-crystal silicon actuators

Abstract

In this paper, we demonstrate an electrostatic RF MEMS switch with a low actuation voltage, which is obtained simply by optimizing the design and fabrication of the robust single-crystal silicon (SCS) actuator, as well as a uniform switch performance. Through the simple approach, the pull-in voltage of the proposed electrostatic switch could be reduced simply and efficiently to approximately 10 V without sacrificing the structural stabilities and degrading the switch performances. For a total of 68 switches on a wafer, the fabrication and measurement yields were obtained to be higher than 94 and 73%, respectively. The switch performances of 50 identical switches except for 4 initially broken and 14 non-actuated switches were successfully characterized. The measured pull-in voltage was 10.7 ± 1.5 V and that of 40 switches (80%) was as low as 12 V. Nevertheless, the 50 identical switches showed considerably good and uniform performances with little deviations in terms of the RF and pull-in voltage characteristics. In addition, self-actuating behavior of the switch was not observed up to the input power of 37 dBm although the actuation voltage was reduced considerably. Low insertion losses of 0.13 ± 0.06, 0.15 ± 0.05, 0.19 ± 0.06 and 0.2 ± 0.07 dB were acquired at 2, 5, 10 and 15 GHz, respectively. The isolation characteristics could be obtained to be 41.25 ± 0.78, 33.25 ± 0.98, 27.17 ± 0.82 and 23.57 ± 0.75 at 2, 5, 10 and 15 GHz, respectively. Numerical calculations and simulations based on the fabricated results of the switches clearly demonstrated that the performance deviations among the tested switches were mainly due to the fabrication errors and not structural deformations.